Implantable medical electrical leads, included in systems that are known in the art for delivering cardiac therapy and/or for providing cardiac monitoring, are often implanted transvenously within a heart of a patient. But extravascular implant sites may be preferred, for example, in those patients where vascular access is difficult, or because transvenous leads can become fibrosed in the heart over time, which makes lead revision and extraction procedures challenging.
FIG. 1 is a schematic showing an access site A for creating a passageway between a patient's diaphragm 19 and xiphoid process 20 of sternum 13, for example, to implant a medical electrical lead on an epicardial surface 6 of the patient's heart, which is enclosed within the pericardial sac 15. After making a superficial incision, an operator may open a passageway between diaphragmatic attachments 18 and diaphragm 19 by using blunt dissection tools and techniques that are known in the art. Then, the operator may employ a piercing tool to pass a guide wire through the pericardial sac 15, also according to methods known in the art. The operator may use fluoroscopic guidance to position a distal portion of the guide wire along a portion of epicardial surface 6, at which a target implant site is located, and then pass a guiding catheter over the positioned guide wire. The guiding catheter then serves as a conduit for delivery of an implantable medical electrical lead to the target implant site, but some difficulty may be encountered by the operator in securing the delivered lead to the implant site.